Vectorially oriented membrane films containing bacteriorhodopsin (BR) on indium-tin-oxide (ITO) conductive glass (achieved by the electrophoretic sedimentation method), and randomly oriented films on ITO glass or CaF2 plate (achieved by natural drying) have been characterized by using polarized Fourier-transform infrared (FTIR) spectroscopy and laser-induced photocurrent measurements. Vectorially oriented and randomly oriented membranes gave a similar average or-helical orientation of similar to 30 degrees with respect to normal membranes, as obtained from polarized FTIR spectra. Under pulsed laser excitation, two oppositely oriented BR films, with membrane surface either extracellular (EC) side or cytoplasmic (CP) side facing ITO (ITO/EC-CP vs. ITO/CP-EC), gave a photocurrent component pair, B1/B2, in a similar amplitude but with opposite polarity, whereas randomly oriented him simply shows very small B1/B2 signals. Thus, photocurrent measurement seems to be an effective and reliable way for the recognition of BR membrane orientation.